Question

I have a GUI program that is executed by default via javaw.exe using a startup wrapper created with Launch4j.

This program can also be executed from command-line and then print output to the console.

How can I detect if a console is visible, hence that the text I output via System.out.println() is visible?

From my understanding this depends on whether the program has been started via Javaw/wrapper or directly by java -jar myprog.jar. Is there a way to distinguish both starts methods from withing the program?

Answer 1

If System.console() returns null, there’s no console, which happens when you start the program with javaw instead of java. Example:

import javax.swing.JOptionPane;

public class Example {
    public static void main(String[] args) {
        if (System.console() != null) {
            System.out.println("Hello on the console");
        } else {
            JOptionPane.showMessageDialog(null, "Hello, there's no console");
        }
    }
}

Try compiling this and then starting it with either java Example or javaw Example.